1. Field of the Invention
The present invention relates in general to the art of detecting a pressure pulse wave of a living subject by pressing a pressure pulse wave sensor against a skin surface of the subject and in particular to a pressure pulse wave transmitting sheet for being interposed between the sensor and the skin surface.
2. Related Art Statement
There is known a pulse wave detecting device including (a) a pressure pulse wave sensor having a press surface and adapted to be set on a skin surface of a body portion (e.g., wrist) of a patient so as to be positioned directly above an arterial vessel (e.g., radial artery) of the patient, and (b) pressing means for pressing the sensor against the artery via the skin so that at least one pressure sensing element provided in the press surface of the sensor detects a pressure pulse wave transmitted from the artery to the press surface in synchronism with heartbeat of the patient and generates an electrical signal representative of the detected pressure pulse wave (hereinafter, referred to as the "pulse wave signal"). An example of this device is disclosed in Japanese Utility Model Application filed by the Assignee of the present application and laid open under Publication No. 3-27208 on Mar. 19, 1991.
However, in the above detecting device, the pressure pulse wave sensor is directly pressed against, or held in direct contact with, the skin of the patient, and accordingly the patient may suffer from pain due to the direct pressing or contact of the sensor with the skin. In addition, in the case where the detecting device is applied to a thin patient, the sensor may not engage deeply with, or bite deeply into, the skin of the patient and consequently the sensor may move or slip off the position directly above the artery.
Furthermore, in the case where the skin on which the sensor is set is covered with hair stiffer than the skin, the pulse wave signal generated from the sensor may adversely be influenced by the hair. More specifically, the magnitude of the pulse wave signal may inaccurately be increased due to the pressed contact of the hair with each pressure sensing element supported by the press surface of the sensor.